GNSS does work, but it can take a pretty long time to acquire an initial location without PSDS and SUPL. It also uses much more battery. This can especially become an issue if you want to share your live location with somebody, or record your workout over a longer period of time. There are technologies like A-GNSS (Assisted GNSS) that use SUPL (Secure User Plane Location) and PSDS (Predicted Satelite Data Service), but these also require you to send your location to a third party (the default SUPL service on Android is supl.google.com, which is definitely much worse for your privacy than any NLP). GrapheneOS hosts a proxy at supl.grapheneos.org, which is much more private (see GrapheneOS's privacy policy for all their network services: https://grapheneos.org/faq#privacy-policy). PSDS isn't much better, as it's usually provided by the manufacturer of your phone's SoC (e.g. Qualcomm, Broadcom or Samsung). PSDS also sends a lot of data to the service, including SoC serial number and information on the phone including manufacturer, brand and model. GrapheneOS improves the privacy of PSDS (you can read more about all of this at https://grapheneos.org/faq#default-connections), but I still don't see how this would be better than a privacy-friendly network location provider. beaconDB is still in a pretty early phase of development, but it's likely going to be used by GrapheneOS when it becomes more stable. It's also likely, that the GrapheneOS project will either host their own proxy for the public beaconDB service, or their own server using beaconDB data. That way, it would be even more private, and it would be covered under Graphene's privacy-policy, which is essentially just the EFF's privacy-friendly Do Not Track (DNT) policy.